This invention relates generally to inter-surface connectors for printed circuit boards and more particularly to an eyelet-type connector which connects one surface of a printed circuit board to the other surface thereof through a hole in the printed circuit board.
There are several known ways of connecting one surface of a printed circuit board to the other surface through a hole therein, which include, for example, eyelets of various types, standoff terminals, clinched jumper wire connections which are in essence, a solid wire extending through the hole and then bent over to make contact with the printed circuit board surfaces, and others.
All of the foregoing inter-surface connectors have a common problem. Certain types of printed circuit board material, particularly the paper laminated type, expands when heated. Since most inter-surface connectors, such as those mentioned above, are soldered to opposite surfaces of a board to complete the connection through the hole, the board is heated and expands. Upon cooling the solder will solidify while the board is still heated and expanded. The board will then continue to contract and at a faster rate than the metal parts, including the solder and the connector, since the coefficient of expansion of the board is considerably higher than that of the metal and solder ordinarily used in the assembly. Thus, when the board contracts it frequently will break the bond between the solder and the conductive pad on the surfaces of the printed circuit board. Sometimes the solder joint itself will crack. In either event, poor electrical connection is obtained, and a high resistance connection or open circuit will result.